1. Field of the Invention
The present invention relates generally to water purification apparatus and more particularly to small-capacity water purification apparatus which are particularly adapted for home use.
2. Discussion of the Prior Art
Because of the poor quality of potable water in many parts of the world and the deteriorating quality of potable water in many other parts of the world, including the United States, small, highly efficient water purification systems suitable for home use are increasingly in demand. In this country the demand for such water purifying apparatus is fueled by public concern about the contamination of water supplies by industrial waste, agricultural pesticides and indiscriminate chemical dumping. Moreover, even in regions where the water is considered relatively safe to drink, the taste is often bad due to public water treatment additives, and home treatment to improve the taste is desirable.
Accordingly, various types of in-home, potable water treatment apparatus are on the market. Simple, relatively inexpensive apparatus, utilizing, for example, activated charcoal are available. These types of water filtering apparatus are typically installed directly in a water outlet line and may be connected to enable water flow selection either through or bypassing the filter. Usually, rather minimal improvement in water quality is achieved by such low cost filtering apparatus, although water clarity may be improved by the removal of suspended particulate matter. Ordinarily most bacteria and chemical contaminants are not removed by such simple apparatus.
True water purification apparatus, which remove bacteria and most chemical contaminants, usually use reverse osmosis filters of a micropore membrane type, and are more sophisticated, and hence, usually more expensive, than the above-mentioned, activated charcoal or similar types.
Typically, in reverse osmosis water purification systems, the filter element is connected, by a line tap, to a household water line, the line pressure forcing water through the filter. Because water flow rate is restricted through the filter, the purified water is usually discharged from the filter into a storage tank having a several gallon capacity. During water non-use periods, the storage tank is filled from the filter and during periods of water use, water is drawn from the tank.
Ordinarily water pressure is maintained in the storage tank by pressurized air so as to enable full utilization of purified water in the tank, since water line pressure would otherwise be attained in the tank only during periods of non-use when the tank was full. Unless pressurized, as soon as water withdrawal from the tank was started, water pressure at the point of use would rapidly diminish.
An automatic back pressure shut off may be provided to stop flow of untreated water through the reverse osmosis filter when the tank is filled. Filtered-out impurities are discharged from the filter, with some of the in-flowing water, to a household drain line.
Heretofore, to the applicants' knowledge, the storage tanks used in the described reverse osmosis water purification systems have used a plastic bladder or diaphragm to separate the pressurizing air from the purified water. This has been done so as to prevent escape of pressurizing air from the tank when, by use, the water level in the tank is reduced to a minimum level.
Use of such plastic bladders or diaphragms in the purified water storage tank has, however, caused various problems. Diaphragms are particularly difficult to seal in the tank and if the diaphragm or bladder leaks, pressurizing air escapes from the tank when the water level is reduced in the tank. Expensive repairs are then necessary. Furthermore, the plastic materials commonly used for the bladders or diaphragms are ordinarily a source of contaminants which tend to make the purified water taste bad. This is particularly the case when a bladder or diaphragm starts going bad or "sour". Accordingly, a secondary, flow-through filter, for example, using activated charcoal, is installed between the storage tank and the household tap to improve the taste of the water. Nevertheless, contaminants not removable by the secondary filter may be introduced into the purified water by the bladder or diaphragm and the effectiveness of the water purification system may accordingly be impaired.
Another disadvantage associated with heretofore known household-type water purification apparatus is the difficulty in determining when the main (reverse osmosis) filter should be replaced. It is known that the reverse osmosis filters used in household type water purification gradually lose their effectiveness, the rate of loss being dependent upon the quality of the water being purified and upon the amount of water processed by the filter, that is, by the amount of purified water used.
Inasmuch as the reverse-osmosis filters are not ordinarily visible to, or readily accessible by, the user, it has heretofore been very difficult to determine when the reverse osmosis filter should be replaced. Moreover, it has been difficult even to determine if the reverse osmosis filter of a water purification apparatus is properly operating upon the system's initial installation or after the system has been serviced. Typically, filter replacement intervals, which may be too short to be economical or too long for effective filter operation, according to water quality or usage, are specified. Alternatively, the reverse osmosis filters are replaced when the production rate of purified water becomes perceptibly slower than normal, which may be difficult to determine if the use rate is low, or when the quality of the purified water becomes noticably bad, which may, in some instances, occur only after the level of contaminants in the water has risen to unacceptable limits.
As a result, improvements to home-type water purification apparatus are needed, and it is an object of the present invention to provide water purification apparatus which eliminates the necessity for using a bladder or diaphragm in the storage tank and which enables easy determination by the user as to the filtering condition of the filter element and when the filter should be replaced.
Another object of the present invention is to provide a water purification apparatus for household use in which the pressurizing gas and purified water in the storage tank are in direct contact with one another and in which means are provided for preventing escape of pressurizing gas from the storage tank when the usable amount of purified water has been drawn from the tank.
A further object of the present invention is to provide a reverse osmosis-type water purifying system for household use in which the pressurizing gas and purified water in the storage tank are in direct contact with one another, and in which means are provided for enabling easy determination by a user as to the condition of the filtering element and when the filtering element should be replaced.
Other objects, features and advantages of the present invention will be readily apparent from the following detailed description when taken in conjunction with the accompanying drawings.